The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
An internal combustion engine combusts a mixture of air and fuel that produces drive torque and exhaust gas. The exhaust gas may contain emissions including nitrogen oxides (NOx), carbon monoxide (CO), and hydrocarbons (HC). An exhaust treatment system converts the emissions to carbon dioxide and water using a catalytic converter.
The catalytic converter includes a catalyst that stores oxygen and HC. The catalyst becomes active when the catalyst temperature is greater than or equal to an activation temperature. While the catalyst temperature is less than the activation temperature, the emissions may exit the exhaust system. The catalyst temperature may be increased by raising the temperature of the exhaust gas.
The engine may increase the exhaust gas temperature using various methods. For example, the engine may increase fueling and decrease spark advance to increase HC entering the catalyst. The HC may combust in the catalyst and raise the catalyst temperature. Increasing fueling and decreasing spark advance may result in higher HC emissions, decreased fuel economy, and unpleasant fuel odors.